This invention relates generally to expansion valves for use in refrigeration/reclaim systems and particularly to a thermostatic expansion valve which can modulate valve flow independently of the system refrigerant.
In a conventional refrigeration or reclaim system of the type which includes a compressor, a condenser and an evaporator there is a need for a flow control device to meter liquid refrigerant into the evaporator at a precise rate. Various devices have been used to accomplish this flow control including fixed restrictor and variable restrictor devices. The former type of device, which utilizes capillary tubes and fixed orifices, provides precise metering but only under specific operating conditions. The latter types of device is more versatile and senses conditions within the refrigeration system to open or close the flow area to match the liquid refrigerant flow to existing conditions.
The most common form of variable restrictor device is the standard thermostatic expansion valve which senses the evaporator outlet temperature by means of a thermal bulb which is charged with a temperature sensitive gas or liquid refrigerant and creates a corresponding pressure acting on one side of the expansion valve motor element, usually a diaphragm. At the same time evaporator pressure is conducted from the evaporator through the valve and applied to the other side of the expansion valve motor element. In addition, it is customary to install a compression spring under the motor element which provides a force balance across the motor element and modulates the valve pin with respect to the valve port thereby controlling the refrigerant flow area. Valves of this type are manufactured by Sporlan Valve Company of St. Louis, Mo. and are disclosed in U.S. Pat. Nos. 2,573,151, 3,252,297, 3,742,722 and 4,750,334.
A primary problem with expansion devices of this type is that the sensing bulb charge must be selected to match the system refrigerant.
This thermostatic expansion valve solves this, and other problems, in a manner not disclosed in the known prior art.